Loom with an insertion brake

ABSTRACT

A loom with an insertion brake disposed between a yarn feeder and the shed of the loom, which insertion includes a movable brake element, which is capable of movement between two fixedly disposed yarn guides from a position of rest on one side of the yarn to an operative position on the other side of the yarn. The movable brake element is connected to a driving motor, the excitation of which is controlled by an electronic system, in which at least one program for the time and the position of the movable brake element is incorporated. The electronic system includes a position detection sensor for sensing the instantaneous position of the brake element. The electronic system compares the instantaneous brake element position with the position which is desired according to the program and, if a deviation is established between the sensed instantaneous position and the desired position, controls the amount of current being supplied to the motor in such a manner that the deviation is at least largely eliminated in combination with the reactive force of the yarn.

This is a nationalization of PCT/NL00/00047, filed Jan. 21, 2000 andpublished in English.

FIELD OF THE INVENTION

The present invention relates to a loom with an insertion brake which isdisposed between a yarn feeder and the shed of the loom, which insertionbrake comprises a movable brake element, which is capable of movementbetween two fixedly disposed yarn guides from a position of rest on oneside of the yarn to an operative position on the other side of the yarn,wherein the movable brake element is connected to a driving motor, theexcitation of which is controlled by an electronic system, wherein atleast one programme for the time and the position of the movable brakeelement is incorporated in said electronic system.

BACKGROUND OF THE INVENTION

In looms, in particular air looms, the weft yarn is carried into theshed from a yarn feeder at a high velocity during the insertion process.Near the end of the insertion process, the yarn movement is brakedabruptly by a braking element on the yarn feeder, wherein the kineticenergy contained in the weft yarn is converted into tension energy inthe yarn. High tension peaks may occur in the yarn thereby, which mayhave various undesirable consequences and which may in some cases evenlead to yarn breakage.

In order to obviate the occurrence of such a tension peak and/or damp itat least partially, EP 0 356 380 discloses a loom wherein an insertionbrake is disposed between the yarn feeder and the shed of the loom,which insertion brake comprises a driven, movable brake element, whichis capable of movement between two fixed yarn guides from a position ofrest, wherein the yarn is not passed over the fixed yarn guides, or onlyto a small extent, to an operative position, wherein the yarn is passedover the yarn guides to a greater extent. The movable brake element isthereby driven in such a manner that the brake element is first movedfrom its position of rest to a maximum stroke position at the end of theinsertion process or shortly therebefore. Then the brake element isreturned from its maximum stroke position to a reduced stroke positionunder the influence of the reactive force of the yarn, wherein thekinetic energy contained in the yarn is reduced and the occurrence of atension peak is obviated or at least damped. In the prior art loom allthis is according to one embodiment achieved in that the movable brakeelement comprises an elastic part, which is pressed down by the reactiveforce of the yarn following a maximum stroke of the brake element,whereby kinetic energy from the yarn is stored in said elastic parts Inanother embodiment, the brake element is controlled by a linear magneticmotor, which is so controlled that the brake element is only moved toits maximum stroke position upon major excitation of the motor, afterwhich the degree of excitation is reduced and the reactive force of theyarn is capable of returning the brake element against the motor force,whereby reduction of kinetic energy in the yarn takes place again, sothat the tension peak is damped in this manner as well. In bothembodiments an interaction between the reactive force of the yarn and amechanical or electrical force of the brake element takes place,therefore. This interaction may lead to malfunction, especially athigher operating speeds of the loom, so that an optimum damping of thetension peak that occurs cannot be achieved.

Another embodiment of a loom of the kind to which the present inventionrelates is disclosed in EP 0 155 431. In this prior art loom, the brakeelement which is capable of movement between two fixed guides is alever, whose movements are controlled by a cam driving unit. Aposition-time diagram is stored on the circumferential surface of thecam in question, according to which the movable brake element'spositions are controlled during the insertion process. Such mechanicalcontrol of the movable brake element is satisfactory per se forlower-speed looms, but one drawback is the fact that constantly the sameposition-time diagram is gone through for each insertion. Generally suchmechanical control is not sufficiently flexible for quickly varyingoperating conditions, whilst it is furthermore difficult to adapt tovarying yarn qualities, for example. Furthermore, this mechanicalcontrol of the brake element is fairly inelastic (rigid), so thatproblems may arise in case of sudden thickenings in the yarn.

In order to make a loom of the above kind more flexible and more easilyadaptable to varying operating conditions, EP 0 605 531 presents a loomwherein the movable brake element is driven by a fast-response steppingmotor or DC motor, which is controlled by an electronic control device,which comprises a programme section incorporating a variable programmefor time and position of the brake element, at least between insertions.The connection between the motor and the brake element is inelasticthereby, and the driving force of the motor is larger than the maximumreactive force of the yarn at all times, so that it is possible to gothrough any position-time diagram for the brake element that may bedesired. One drawback of this prior art loom is the fact that the brakeelement control is still rigid, so that problems may arise after allwhen sudden thickenings are encountered in the yarn.

From Dutch laid-open patent application No. 6712481 a yarn brake isknown which comprises a stationary brake element and a movable brakeelement. The movable brake element is thereby driven by a moving coilmotor, which is excited via an electronic system, wherein a positiondetection sensor is incorporated in the electronic system, whichposition detection sensor senses the instantaneous position of themovable brake element. The amount of current being supplied to themoving coil motor thereby depends on the position of the movable brakeelement as sensed by the position detection sensor, all this in such amanner that the final tension of the yarn will remain constant, also inthe case of variations in the initial tension. This yarn brake is agenuine yarn tension regulating device, therefore.

Another device for regulating the yarn tension in looms is disclosed inEP 0 467 059. In this device the movable brake element is a two-armedrotary lever, one end of which is movable between two fixed yarn guidesand the other end of which carries a magnet coil, which co-acts with twospaced permanent magnets of a linear electric motor. In a lever positionwherein the yarn is passed over the fixed guides, said permanent magnetsproduce an effect like a spring. The yarn tension thereby exerts areactive force on the lever, which is compensated by the degree ofexcitation of the linear electric motor. The instantaneous yarn tensionis calculated on the basis of the degree of excitation of the linearelectric motor. The electronic control system for the linear motorfurthermore includes a position detection sensor, which continuouslysenses the instantaneous position of the lever. The instantaneous yarntension calculated from the degree of excitation of the linear motor iscompared with a desired yarn tension for each position, and in case of adeviation the degree of excitation of the linear motor is changed. Thusthe yarn tension can be regulated in such a manner that it conforms to aspecific desired position-tension diagram. Furthermore the linear motorof this prior art device can also be excited in such a manner that thebrake element takes up positions which are required for drawing back theyarn at the end of the insertion process.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a loom wherein themovable brake element is controlled in a flexible and very precisemanner whilst exhibiting sufficient elasticity to be able to cope withsudden variations in the yarn quality or the yarn thickness.

In order to accomplish that objective, the loom according to theinvention is characterized in that the electronic system comprises aposition detection sensor for sensing the instantaneous position of thebrake element, wherein the electronic system compares the instantaneousbrake element position with the position which is desired according tothe programme and, if a deviation is established between the sensedinstantaneous position and the desired position, controls the amount ofcurrent being supplied to the motor in such a manner that said deviationis at least largely eliminated in cooperation with the reactive force ofthe yarn.

The brake element used in the loom according to the invention can bedriven by any type of electric motor, wherein the force to be exerted bythe motor upon movement in the direction of its maximum stroke positiononly needs to be a little larger than the reactive force exerted by theyarn, whilst the motor force may even be smaller than the reactive forceof the yarn upon return of the brake element from its maximum strokeposition, whereby the reactive force of the yarn causes the brakeelement to move back. Possibly, a negative motor force can be employed,if desired, so that the return movement of the brake element is not onlythe result of the reactive force of the yarn, but it is also assisted bythe motor. As a result, the return movement of the brake element willtake place at a higher velocity. The electronic system controls themotor force in such a manner that the brake element position sensed bythe sensor is compared continuously or at intervals with the position asdesired by the programme, and in that the motor force is so controlledin case of a deviation that this deviation is eliminated. In this mannerthe desired position-time diagram of the movable brake element isfollowed precisely, whilst the brake element is not controlled in anundesirable, rigid manner. Sudden thickenings that may occur in the yarncan effect an instantaneous movement of the brake element, with adeviation occurring between the desired position and the instantaneousposition, which deviation is subsequently eliminated. Yarn breakage willbe rare.

Any suitable type of motor, for example a hydraulic, pneumatic orelectric motor, can be used for driving the brake element.

According to another embodiment, the movable brake element is made up ofone end of a lever which is rotatable about a shaft, wherein said shaftis linked to a rotary solenoid motor. The advantage of such a motor isits low moment of mass inertia and short response time.

Another advantageous embodiment, wherein the movable brake element ismoved from its position of rest to its maximum stroke position shortlybefore the end of the insertion process, is characterized in that theelectronic system excites the driving motor sooner and/or more stronglyas the end of the insertion process comes earlier, so that the maximumstroke position is reached more quickly. In this manner it is achievedthat the maximum stroke position is reached sooner at higher yarnspeeds, so that the reduction of the kinetic energy contained in theyarn is initiated sooner, so that the feared tension peak will be dampedin time and to a sufficient degree at higher yarn speeds as well. Theuse of a yarn winding counter on the yarn feeder makes it possible tocount the number of windings being unwound from the yarn feeder,wherein, when detection of a predetermined number of windings beingreached before the end of the insertion process causes the electronicsystem to excite the movable brake element. In this manner it ispossible during the insertion process already to adjust the moment ofdriving of the brake element to the fact that the end of the insertionprocess will be reached sooner or later.

Another advantageous embodiment of the loom according to the inventionis characterized in that the mass inertia of the movable brake has beenselected to be so low that the force being exerted on the brake elementis capable of moving the brake element upon detection of irregularitiesin the yarn. It is noted that the term mass inertia of the movable brakeelement is to be understood to mean the mass inertia of the brakeelement itself and also of all the parts connected thereto. In thismanner it is achieved that a thickening that may occur in the yarn willbe capable of moving the brake element when it strikes against saidbrake element, which movement will be sensed by the position detectionsensor, after which the control system will directly eliminate thedeviation between the desired position and the instantaneous position. Athickening or other yarn irregularity can thus pass the brake elementpractically without impediment, without this leading to impermissiblyhigh tension peaks in the yarn.

In looms comprising insertion brakes of the kind to which the presentinvention relates, the position detection sensor produces an electricsignal of a specific magnitude for every current position of the brakeelement. The control system recognises these electric signals as ameasure of a specific current position of the brake element. This means,therefore, that an electric sensor signal of one specific magnitude isassociated with every current position of the brake element. A problemwhich occurs thereby is that the sensors that are used may exhibit acertain deviation in the magnitude of the signals they generate. Thismight lead to one sensor generating a signal of a different magnitudethan another sensor in one specific current position of the brakeelement, therefore, causing the control system to derive therefrom aposition which does not exactly correspond to the current position ofthe brake element. In order to overcome this problem, another embodimentof the insertion brake according to the invention is characterized inthat the movable brake element is capable of movement between a firststop and a second stop, and in that the electronic system includes acontrol module for adjusting the position detection sensor, wherein thecontrol module first stores a first signal from the position detectionsensor when the brake element abuts against said first stop, and thenrecords a second signal when the brake element abuts against said secondstop, storing the difference between said first and said second signalas a maximum (100%) value of the path through which the brake elementcan travel, after which the module in use converts the signals from thesensor associated with the instantaneous positions of the brake elementto a percentage of said difference signal, from which the instantaneousposition of the brake element follows as a percentage, of the maximumstroke position of the brake element, which momentary position iscompared with the desired position by the electronic system.

When the insertion brake is placed into service or when the sensor isreplaced, the brake is first moved to a position wherein it abutsagainst the first stop (minimum stroke position), after which the firstsignal delivered by the position detection sensor is recorded by thecontrol module. Then the brake is moved to a position wherein the brakeelement abuts against the second position and the second signaldelivered by the position detection sensor is recorded again. Thecontrol module then determines the difference between the first and thesecond signal, which difference will be a measure for the spacingbetween the first and the second stop.

Following that, the brake can be placed into service. In a specificposition of the brake element, the position detection sensor will nowdeliver a signal which is related to the stored difference signal in thecontrol module and which is converted into a percentage of saiddifference signal. Accordingly, this percentage is also a percentage ofthe difference between the minimum (abutment against the first stop) andthe maximum (abutment against the second stop) position of the brakeelement. In this manner reliable information as to the instantaneousposition is obtained.

The position detection sensors can thus be adjusted easily and quicklybefore being placed into service, so that any differences in theiroperation will not effect the further control system of the brake.

It is noted that the brake element is only brought into contact with thesaid two stops when the sensor is being adjusted. During the furtheroperation of the brake, the brake element will move within an range of20-80% of the maximum stroke position between said stops.

In order to be able to verify whether a specific insertion brake isstill functioning sufficiently quickly and accurately after some time, afurther embodiment of the movable brake element is arranged forverifying whether the movable brake element has completed a specificposition change within a specific period of time with a predetermineddegree of excitation. For example, it is possible to verify therewithwhether the brake element has completed a position change of 50-80%within a specific period of time with a predetermined degree ofexcitation. This verification preferably takes place in a range ofmovement of the brake element in which there will be no influencing bythe yarn. Thus it is possible to establish in a simple manner whetherthe friction has so increased, for example due to fouling or otherwise,that the insertion brake no longer meets the requirements made thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail with reference to anembodiment.

FIG. 1 is a schematic front view of an air jet loom.

FIG. 2 is a perspective, schematic view of an embodiment of an insertionbrake.

FIGS. 3a-3 d successively show an example of a time-position diagram ofthe movable brake element; the trend of the excitation of the drivingdevice of the movable element; the trend of the tension in a braked yarnand finally the trend of the tension in a non-braked yarn.

FIGS. 4a and 4 b show another embodiment of an insertion brake.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In an air jet loom R, a weft yarn 1 is fed from a supply drum 4, via aninsertion brake 6, to a main injector 7. The main injector 7 feeds theyarn 1 past scissors 8 to the shed 3 formed by the warp yarns 2, whichhas a width W. Auxiliary blow pipes 9, which are connected to acompressed air pipe 11 via magnetic valves 10, assist the transport ofthe weft yarn through shed 3. After the end of the weft yarn 1 has leftshed 3, it enters the funnel 12 of an extractor 13 and is cut off,wherein the two yarn ends are laid into selvedge devices 14 disposed oneither side of the shed. The figure furthermore shows that thecompressed air pipe 11 is connected to a compressed air generator 16 viaa pipe 15, whilst the figure also shows a drum 18 for the finishedproduct, which drum is disposed between side walls 17.

Insertion brake 6 is built up of 2 fixedly disposed yarn guides 20,between which a movable brake element 21 is disposed. The movable brakeelement 21 is connected to a driving device 23 via a lever 23. Theinsertion brake 6 furthermore comprises a sensor 24 for sensing theinstantaneous position of the movable brake element 21. The loomfurthermore comprises an electronic control device 25, which includes aprogramme section 26 in which at least one time-position programme forthe movable brake element 21 is stored. The position detection sensor 24continuously transmits the sensed instantaneous position of the movablebrake element 21 to the electronic control device 25 via line 27, whichcontrol device 25 compares said instantaneous position with the desiredposition in programme section 26, after which, in case of a deviationbetween the sensed instantaneous position and the desired position, theelectronic device varies the excitation of the driving device 23 vialine 28 in such a manner that the detected deviation is at leastsubstantially eliminated.

A stop element 30 is furthermore operative on supply drum 4, which stopelement is pressed against the supply drum surface at the end of theinsertion process, that is, when the end of the weft yarn has reachedthe end of the shed, so that further unwinding of the yarn from thesupply drum is stopped.

One embodiment of an insertion brake which can be used in the loomaccording to FIG. 1 is shown in FIG. 2. Said figure shows the manner inwhich a lever 21 in the form of a fork is capable of movement betweentwo fixedly disposed yarn guides 20. Lever 21 is fitted with a block 31on its other side, which is mounted on a shaft 32 of a solenoid motor33. Block 31 is fitted with a magnet 34, which cooperates with a sensor35. Although a solenoid electric motor is used for driving the movablebrake element 21 in this embodiment, it will be apparent that also othertypes of electric motors can be used, even hydraulic or pneumatic motorsmay be used.

The operation of the insertion brake according to the invention will nowbe explained in more detail with reference to FIG. 3. As already saidbefore, the moment yarn 1 reaches the end of the shed, that is, themoment stop element 30 comes into operation, very high tension peaksoccur in yarn 1 in looms which do not employ an insertion brake, becausethe kinetic energy contained in the yarn converts into tension. Thetrend of the yarn tension, that is, in the situation wherein no brake isused, is schematically shown in FIG. 3d, from which it is apparent thatduring the first part of the insertion process the tension in the yarnis at a low level, after which the tension runs up very high at momentS, which is the moment the stop element becomes operative. The insertionbrake is intended to remove the kinetic energy contained in the yarnaltogether or partly before the stop element 30 becomes operative. Inorder to achieve this with the desired precision, the movable brakeelement must follow a precisely defined motion pattern. These desiredmotion patterns may vary with different yarn qualities and differentoperating conditions. A time-position diagram of the movable brakeelement 21 for a specific yarn type is shown in FIG. 3a. The figureshows, seen from the left-hand side, the brake element 21 to occupy itsposition of rest first, in which position the yarn is hardly deflectedfrom its path, if at all, and at moment R, that is, some time beforemoment S at which the stop element becomes operative, the brake element21 must be moved from its position of rest to its maximum strokeposition according to a time-position line which is to be followedexactly. The time-position diagram for brake element 21 is stored inprogramme section 26 of the electronic control device 25. Theinstantaneous position of the brake element 21 is continuously sensedand transmitted, via sensor 24, to the electronic device 25, where saidinstantaneous position is compared with the position as desiredaccording to the time-position diagram. Upon detection of a deviationbetween the desired position and the instantaneous position, theelectronic device 25 will control the excitation of the driving unit 23in such a manner that the deviation will be at least substantiallyeliminated. The trend of the excitation of the driving device 23 as itoccurs in practice is shown in FIG. 3b. The trend of the tension in theyarn as it occurs when an insertion brake according to the invention isused is shown in FIG. 3c, from which it appears that the tension peaksthat now occur are only very small, in any case much smaller than in thesituation of an non-retarded yarn as shown in FIG. 3d.

In the embodiment which is discussed with reference to FIG. 3, only onepossible time-position diagram for the movable brake element isillustrated in FIG. 3a. It will be apparent that several time-positiondiagrams, for example for different yarn types, may be stored in theprogramme section of the electronic device.

The moment the end of the insertion process is reached will varyslightly as the speed at which the yarn is carried through the shedvaries. This means that also moment S, at which the stop element becomesoperative, will exhibit some degree of variation. In order to take thisinto account, the electronic device 25 will adapt the point R at whichthe brake 21 is put into operation to said variation and shift it tosuch an extent that the distance between points R and S will remainsubstantially constant. Possibly, the electronic device can adjust theexcitation of the driving device so that the gradient of the linebetween the moment the brake 21 is put into operation and the moment itreaches its maximum stroke position will become steeper or less steep asmoment S occurs sooner or later, respectively. Brake 21 thus ensuresthat the kinetic energy contained in the yarn is reduced accurately andin time.

The signal which tells that the end of the insertion process is nearing,the signal of point R, therefore, can for example be delivered by asensor which counts the number of windings being unwound from supplydrum 4. One or two windings before the end of the insertion process,said sensor signals to the electronic control device that point R hasbeen reached, whereupon the brake is excited. Possibly such a signal canalso be obtained by means of one or more sensors disposed in the shed,which sense the passage of the yarn end at a location some distance awayfrom the end of the shed and transmit this as a signal of point R to theelectronic control device. Although the electronic control device isrepresented as a separate block in this embodiment, it will be apparentthat it may form an integrated part of the overall control apparatus ofthe loom.

According to the invention, the brake is so arranged that the moment ofmass inertia of the brake element 21 and the parts connected thereto isso low that any irregularities in the yarn, such as thickenings, whichstrike against the brake element 21, are capable of moving the brakeelement 21 temporarily, so that such thickenings can pass the brakeelement without any undesirably high yarn tensions occurring.

The sensor 24, together with the electronic system 25, will detect adeviation between the instantaneous position and the desired position inthat case and immediately undertake a control action in order to offsetthe deviation between the instantaneous position and the desiredposition.

Thus an insertion brake is obtained which exactly follows a prescribedtime-position diagram and which still is sufficiently flexible to beable to cope with operating conditions that may suddenly occur.

Although the insertion brake according to the invention is describedherein as being used in an air jet loom, said brake can also be used inwater jet looms and other types of looms whilst retaining itsadvantages.

FIG. 4 schematically shows an insertion brake similar to the one whichis shown in FIG. 2, wherein a first stroke-limiting stop 41 is disposedon one side of the movable element 21 and a second stop 42 is disposedon the other side thereof. As is furthermore shown in the figure,position detection sensor 35 is connected to the schematically indicatedelectronic control device 25 including the aforesaid programme section26 of the time-position programme as well as a control module 43 foradjusting the position detection sensor 35 and a function verificationmodule 44 for verifying the correct functioning of the brake. When thebrake is placed into service, or following the replacement of sensor 35,the movable brake element 21 is first moved to a position in which itabuts against first stop 41. In this position, position detection sensor35 will deliver a first (zero) signal S1, which is supplied to andstored in control module 43. Then the movable brake element 21 is movedto a position in which it abuts against a second stop 42, wherebyposition detection sensor 35 delivers a second signal S2 for the maximumstroke position of the brake element, which signal is likewisetransmitted to control module 43. In control module 43 the differencebetween S1 and S2 is determined, which difference signal is a measure ofthe total stroke (100%) of the brake element, therefore. Then the devicecan be placed into service, whereby the position detection sensordelivers a signal for every current position. Each of said signals isnow converted in module 43 into a percentage of the difference betweensignals S1 and S2, and thus into a percentage of the total stroke (100%)of the brake element. All this is graphically represented in the diagramof FIG. 4b, wherein the spacing between stops 41 and 42 is shown on thehorizontal axis, whilst the vertical axis shows the signals that aregenerated by the position detection sensor 35. It will be apparent fromthis diagram that a signal S3 which is delivered upon a specific currentposition 47 represents a certain percentage of the difference between S1and S2. This percentage is converted in module 43 into a similarpercentage of the distance between position 41 and position 42, whichamounts to position 47, therefore.

When a new sensor 35 is fitted, this new sensor may generate slightlyhigher or lower signals, the trend of which signals will be asillustrated in dotted lines 45 or 46 in FIG. 4b. Although these signalswill be higher or lower than the signals obtained with the previoussensor, the same percentages will nevertheless be obtained, due to theconversion process as explained before, so that eventually the correctposition will be obtained. Thus, a first sensor will generate a signalS3, which more or less corresponds to 50% of the difference between S1and S2, from which it results that position 47 amounts to approximately50% of the stroke between 41 and 42. Another sensor will generate asignal S4 or S5, which will also correspond to 50% of the differencebetween the associated minimum and maximum stroke position signals. Alsoin this case this will result in 50% of the difference between theminimum and the maximum stroke position, that is, in position 47. Thesame takes place for every current position of the brake element.

Thus an insertion brake has been obtained wherein the influence ofdeviating sensor characteristics on the control system is eliminatedcompletely independently by initial adjustment of the sensors.

After having been placed into service, the movable brake element willnot come into contact with the stops 41 and 42 any more, but it willmove within a range of 20-80% of the maximum stroke. In order to be ableto verify whether the brake is functioning properly, it can beestablished via control module 44 whether the movable brake elementmakes a specific stroke within a specific period of time, for examplestroke amounting to 50-80% of the maximum stroke.

What is claimed is:
 1. A loom with an insertion brake disposed between ayarn feeder and a shed of the loom, said loom comprising: a movablebrake element movable between two fixedly disposed yarn guides from aposition of rest to an operative position, the movable brake elementbeing connected to a driving motor, excitation of the driving motor bycurrent being controlled by an electronic system, at least one programfor a predetermined time and a predetermined position of the movablebrake element being incorporated in said electronic system, theelectronic system including a position detection sensor for sensing aninstantaneous position of the brake element and generating aninstantaneous brake element position signal, the electronic systemcomparing the instantaneous brake element position signal with a desiredpredetermined position of the movable brake element according to theprogram and, if a deviation is established by the electronic systembetween the sensed instantaneous brake element position and the desiredpredetermined position of the movable brake element, the electronicsystem controlling an amount of current being supplied to the drivingmotor so that said deviation between the sensed instantaneous positionof the brake element and the desired predetermined position of themovable brake element is at least largely eliminated.
 2. The loomaccording to claim 1, wherein the movable brake element includes one endof a lever rotatable about a shaft, said shaft is linked to a rotarysolenoid motor.
 3. The loom according to claim 1, wherein the movablebrake element is movable from the position of rest to a maximum strokeposition by the electronic system controlling the amount of current tothe driving motor so that the maximum stroke position is reachedquickly.
 4. The loom according to claim 1, wherein a mass inertia of themovable brake element is low so that a force exerted on the movablebrake element is capable of quickly moving the movable brake elementupon detection of irregularities in the yarn.
 5. The loom according toclaim 3, wherein the movable brake element is movable between a firststop and a second stop, and the electronic system includes a controlmodule for adjusting the position detection sensor, the control modulefirst storing a first signal from the position detection sensor when themovable brake element abuts against said first stop, and the controlmodule records a second signal when the movable brake element abutsagainst said second stop, a difference signal between said first andsecond signal is stored as a maximum value of a path through which themovable brake element travels, the control module converts theinstantaneous brake element position signal to a percentage of saiddifference signal, from which the instantaneous position of the movablebrake element follows as a percentage of the maximum stroke position ofthe movable brake element, which momentary position is compared with thedesired predetermined position by the electronic system.
 6. The loomaccording to claim 1, wherein a specific position change of the movablebrake element is verified for a specified period of time.